T lymphocytes play major regulatory roles in immune responses. Subpopulations of T lymphocytes have been shown to have cytolytic (Tc), helper (Th), and suppressor (Ts) functions. We have obtained clones of cytolytic and helper mouse T lymphocytes reactive with particular alloantigens. The objective of the proposed studies is to characterize the biochemical and functional properties of clones of Tc, Th, and Ts lymphocytes reactive with antigens specified by different regions of the major histocompatibility complex. We will characterize cell surface proteins and glycoproteins of these cloned cells using radiolabeling and gel electrophoresis techniques. Hybridoma antibodies reactive against cloned T lymphocytes will be prepared and used to characterize specific antigen receptors and other cell surface components of T lymphocyte clones. Factors secreted by cells will be characterized biochemically. Determination of structure-function relationships of Tc, Th and Ts lymphocytes should provide insights into the molecular basis for lymphocyte activation and for regulatory interactions among T lymphocytes and other cells.